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Slight knock noise, Yes breaking. Kinda like knocking on a

Customer Question
Hello JA: Hello. What is your...
Hello
JA: Hello. What is your issue regarding?
Customer: Slight knock noise
JA: How would you describe the sound? Does it happen more when you're braking? Shifting gears?
Customer: Yes breaking. Kinda like knocking on a coffee table just one knock and it goes away 2009 c300
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Nothing idk if there is an issue trying to figure it out. What could it be?
JA: Anything else you think the mechanic should know?
Customer: A couple weeks ago some smoke came out of exhaust when i started car but i think was just condinsation
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mercedes Mechanic about your situation and then connect you two.
Submitted: 1 year ago.Category: Mercedes
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Answered in 3 hours by:
7/3/2016
Mercedes Mechanic: Kevin, Master tech replied 1 year ago
Kevin
Kevin, Master tech
Category: Mercedes
Satisfied Customers: 2,447
Experience: Diagnostic technician
Verified

Hi im kevin the knocking you ask about is this every time you brake or only under hard braking ? What colour was the smoke ?how many miles do you do in car does it get used often ?

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Customer reply replied 1 year ago
Kind of under hard breaking. It has 90,000 miles. The smoke was white it hasnt happened since.
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Has the car sat for any periods of time recently ?

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Customer reply replied 1 year ago
Not really no
Customer reply replied 1 year ago
it gets driven at least a couple times a week
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

I mean it sounds as though you haveva rust patch on the front rotors causing your knocking under heavy braking .this will either get better the more brakes are used and will clean surface of rotor .or it will slowly get worse and rotors will need to be replaced to cure .the smoke sounds a lot like condensation if it hasnt happened again no need to worry

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Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Please remember to rate my service and let me know if you need anything elae at all

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Customer reply replied 1 year ago
Hey man i do need rotors they are rusted and breaks squeal when i break. So the knocking gould be caused by the bad rotors?
Customer reply replied 1 year ago
They are rusted pretty bad
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Yeah deffinatly if they are rusty they can make some very heavy knocking noises and in some cases give a vibration through car and steering wheel .replacing them will cure your issue

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Customer reply replied 1 year ago
Sweet thanks a lot man i appreciate it i figured it was something simple but i was a little worried. So its a 2009 c300 with 90,000 miles as long as i keep up with the maintenance i should be good right? Ive never had a mercedes or any luxury car so im hoping it lives up to the hype they say these things last forever lol
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Yes to be totally honest all modern cars last long as maintenence is kept up to date please remember to rate my service

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Customer reply replied 1 year ago
One last question. I finally got the tire pressure correct the care wants 31 but the dash has a "!" Saying correct tire pressure. Do i need to reset it or did i do something wrong?
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Yes you rest tyre pressure through dash board

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Customer reply replied 1 year ago
Yea i keep doing it but it goes back again
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

It goes back ?

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Customer reply replied 1 year ago
The dash says i have a service message, i hit ok, then it says do i wanna reset to new tire pressure i say yes and the "!" Goes away then comes back again within like 10 mins
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Ok so you rest system it accept that its been reset but then comes back ?

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Mercedes Mechanic: Kevin, Master tech replied 1 year ago

ok this sounds like you possibly have a bad tyre valve not giving a correct reading .you will need to have car plugged in to a mercedes scan tool to find which valve is at fault

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Customer reply replied 1 year ago
Ok. Can i do this at autozone with their scanners? Its not a serious issue right
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Not a serious issue at all its more of a convinience issue .autozone may be able to do this for you

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Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Please remember to rate my service

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Customer reply replied 1 year ago
Thanks alot u were great hopefully if i have queations agon i can find u
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

No problem remember to rate and ask for me in future

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Customer reply replied 1 year ago
Ok sounds good
Mercedes Mechanic: Kevin, Master tech replied 1 year ago

No problem

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Mercedes Mechanic: Kevin, Master tech replied 1 year ago

Please remember to rate my service

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Kevin
Kevin
Kevin, Master tech
Category: Mercedes
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